A pipe, tube, or canal that carries gas, liquid, electrical cables, telephone cables, lymph, glandular secretions, water, sap, or air.

(physics) a layer (as in the atmosphere or the ocean) which occurs under usually abnormal conditions and in which radio or sound waves are confined to a restricted path

to enclose in a duct

to channel something (such as a gas) or propagate something (such as radio waves) through a duct or series of ducts